Hi @RAGHU C , welcome to Microsoft Q&A forum.
It seems that you have already added the postgres_fdw extension on the specific database and then want to create foreign data wrapper on the database.
So this issue comes when we try to run the create foreign data wrapper command with users that don't have proper usage rights on postgres_fdw extension.
Please run the below command from the superuser/admin account on the database and then try executing it again.
GRANT USAGE ON FOREIGN DATA WRAPPER postgres_fdw TO <user>;
PG13 Trusted Extension usability issue
Please let us know if this helps or else we can discuss further on the same.
If the answer helps, please mark it 'Accept Answer' as it could help others having similar query.